The search for genetic predisposing factors in developing fetal toxicity of ethanol is continued. Last year we admitted one patient at the Clinical Center with the diagnosis of Fetal Alcohol Syndrome (FAS) under the clinical protocol 83-CH-228. We have continued the recruitment process for FAS patients for this clinical protocol. Recently, a fourth patient with the diagnosis of FAS has been referred from the Kennedy Institute in Baltimore who will be admitted this year for further studies. During the past year we have studied the rate of survival of amniotic fluid cells, derived from pregnancies which yielded FAS babies, in thiamine deficient medium as compared to amniotic fluid cells obtained from normal pregnancies under the same conditions. These studies were conducted in order to delineate whether or not there is any difference in survival between the FAS and normal amniocytes when cultured in thiamine deficient medium. If there is a difference in survival in this medium then the cells will be tested for their transketolase Km for TPP. An assumption was made that cells with a high Km for TPP will be more sensitive to thiamine deficiency states. The preliminary data indicate that amniotic cells derived from FAS pregnancies which were grown in thiamine- deficient medium have a mortality rate of 90% compared to 5% in control cells grown in the same medium for ten days. Since all cells were grown to confluence in thiamine enriched medium there was no difference in the thiamine level in these cells at the beginning of the experiment. Thus, the observed differences seem to be real rather than an artifact of culture conditions. These results may suggest an increased susceptibility to thiamine deficiency among the FAS amniocytes compared to normal controls. Ongoing studies will attempt to ascertain if the FAS amniocytes have a higher Km for TPP for transketolase compared to normal amniocytes in vivo.